I have used the CBS website to compile my own statistics for research. Their data is completely available online as far as I know and you can download the queries you run on the fly in .csv file format, or text or excel. They have various data tables depending on what you find interesting and complete tables of historical data is also available. That said, I think any pilot project would need to start with their publications, which are also available online. These can be freely used as sources for statements. Interesting data for Wikidata could be population statistics of major cities per century or employment statistics per city per century and so forth. See CBS.nl